The present invention generally relates to a field of gathering and reflecting solar energy, and more particularly relates to the heliostat or device that includes an array of solar collectors, either a mirror or photovoltaic, which turns to track the position of the sun in the sky.
With current technologies for solar power, the cheapest mechanisms (according to the NREL Solar Advisor Model https://.nrel.gov/analysis/sam/) are concentrating fields with mirrors shining and concentrating the light on a tower. Approximately half the cost is in the mirrors, and two-thirds of the remainder in a heat powered generator and the remainder in the cost of the tower. Land near desserts with abundant sun is of negligible cost. Towers are typically 45 meters to 90 meters high and the fields can extend hundreds of meters from the tower on the sides.
Heliostats for these systems can sometimes be very large, with mirror assemblies over 10 meters square, and sometimes be quite small but much more numerous, with mirrors on the order of 1 meter square. The former systems need very large and robust tower supports and dual-axis actuators, while the latter type systems require very large numbers of actuators. Both systems, however, require a lot of “non-mirror” material and rather expensive actuators, which increases the cost of the mirror field. In one NREL report, the total cost of the mirror array is on the order of $200/m2. Accordingly, a lower cost point to build solar collectors is desirable in order to compete with other energy sources.